Problem with CGI and embedded html

**Fader_Berg** · 07-11-2016

Hi.

I've got a problem running a cgi-program with embedded html files. It works when running it from the command line, but not when running it in lighttpd. Then I get a 500 - Internal server error [lighttpd errorlog: (mod_cgi.c.607) cgi died, pid: 12688].
What am I doing wrong here?

index.html

Code:

<html>
	<body>
		<h1>Hello world!</h1>
	</body>
</html>

I make a object file of it by

Code:

objcopy -I binary -O elf64-x86-64 -B i386 index.html index.o

main.c

Code:

#include <stdio.h>

extern char _binary_index_html_start[];
extern char _binary_index_html_size;

int main(int argc, char** argv) {

	printf("Content-type: text/html\r\nContent-size: %u\r\n\r\n",
			&_binary_index_html_size);

	fwrite(_binary_index_html_start, 1,
			(size_t) &_binary_index_html_size, stdout);

	return 0;

}

Code:

gcc -o prob main.c index.o

Thanks for help.

**Salem** · 07-11-2016

> extern char _binary_index_html_start[];
> extern char _binary_index_html_size;
It seems very odd that the size of the object in question has a type of char

Assuming this is your mistake, and the size is of type int or size_t, then you need to do something like

Code:

    printf("Content-type: text/html\r\nContent-size: %u\r\n\r\n",
            (unsigned int)_binary_index_html_size);
 
    fwrite(_binary_index_html_start, 1,
            (size_t)_binary_index_html_size, stdout);

**Fader_Berg** · 07-11-2016

I don't know fully how the objcopy object-file and the linker works it out, but that's how you've got to do it to make it work at the command line. I guess the declaration can be of any type.
I find it's odd that you get the size of the data by looking upp the address of the reference, but that's how it works.

Is there other (more logical) ways of embedding data into an executable?

**Fader_Berg** · 07-11-2016

Here's a little more correctly expressed example of main.c. Still the same problem though...

Code:

#include <stdio.h>

extern char _binary_index_html_start[];
extern char _binary_index_html_end[];

int main(int argc, char** argv) {

	size_t len;

	len = _binary_index_html_end - _binary_index_html_start;

	printf("Content-type: text/html\r\nContent-size: %u\r\n\r\n", len);

	fwrite(_binary_index_html_start, 1, len, stdout);

	return 0;

}

**Salem** · 07-11-2016

So does this work as a CGI program?

Code:

int main ( ) {
    printf(
"<html>\n"
"    <body>\n"
"        <h1>Hello world!</h1>\n"
"    </body>\n"
"</html>\n"
);
    return 0;
}

**Fader_Berg** · 07-11-2016

Not without a little modification.

Code:

#include <stdio.h>

int main ( ) {
    printf(
"\r\n\r\n"
"<html>\n"
"    <body>\n"
"        <h1>Hello world!</h1>\n"
"    </body>\n"
"</html>\n"
);
    return 0;
}

That works. Got to give the end-of-header separator to the webserver before the content, or an internal error occures.

I'm using xxd to generate C source of the files instead. That works. So there is something fishy about the objcopy way of doing it. It's strange that the program works flawless in command line, but not as a cgi (in neither Lighttpd ot Apache).

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